Zcash's proposed NU7 upgrade would stop Sprout holders from spending their remaining funds on the upgraded network, even if they keep their keys. Mainnet activation is still undecided, with a decision planned for Oct. 20. Recovering funds before a cutoff can take days of scanning and exposes transaction amounts.
Zcash's proposed NU7 upgrade would close the spending route out of Sprout, its oldest privacy pool, which still held about 22,309 ZEC on Oct. 17. Holders could keep their private key and still lose the ability to move those funds on the upgraded network.
The change is set out in ZIP 2003, a Zcash improvement proposal whose listed owner is Daira-Emma Hopwood. It proposes rejecting version 4 transactions from NU7 onward. Sprout transfers require that format, and neither version 5 nor version 6 supports them.
Mainnet activation is still open
The NU7 deployment specification leaves the activation height unassigned, with a final decision planned for Oct. 20 after testnet experience. Nov. 5 remains the target, conditional on that decision.
Work on the testnet is already running. The Zcash Foundation announced Zebra 7.0.0-rc.0 on Oct. 2, scheduling NU7 at testnet height 4,465,026 around Oct. 6. An Oct. 10 engineering reply confirmed that the testnet had passed activation.
Recovery takes work and exposes amounts
Moving to current wallet software does not necessarily move the coins. Zallet's migration documentation excludes Sprout spending keys and funds from its import process and tells users to preserve their original wallet.dat.
The Argos recovery tool documents a route for holders with a legacy wallet file or standalone Sprout spending keys. For a full-block scan, Argos estimates roughly 280 GB of transfer and potentially days of processing. Its Sprout sweeps land in Sapling, a newer shielded pool.
Exiting also carries a privacy trade-off. Under ZIP 308's migration design, Sprout-to-Sapling value passes through public pool accounting, which exposes the amount without requiring a transparent address.
Why Hopwood wants Sprout retired
Hopwood's proposal argues that Sprout's specialized verification and handling of private notes still add work to live transaction acceptance despite little use. ZIP 2003 also warns that spending may never be restored, although it allows the theoretical possibility of re-enabling version 4 transactions.
If the Oct. 20 decision approves NU7 and assigns a mainnet height, Sprout holders would need to confirm a valid migration before that height.
Source: CryptoSlate
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